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FXeOTeF5 A Derivative of Xenon Difluoride.

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This stabilizing effect is in contrast to the quite obvious
destabilizing effect of simple alkyl groups on these anionic
groups [51. Only the tert-butyl group exerts an influence akin
to that of trialkylsilyl groups. This led Seyferth et af.121 to
reject an interpretation that attributes the stabilizing properties of silyl substituents on ylidic carbanions to a (2pc +
3 d ~ i ) reffect, although they and other authors[3.41 had
originally preferred this explanation. The objection that the
observed phenomena could be attributed solely to steric
effects [2J could not initially be discounted.
In order to come to a decision we have now undertaken the
synthesis of silyl-substituted ylids containing simple silyl
(H3Si-) instead of the extremely bulky trialkylsilyl groups.
The following scheme shows a typical preparative procedure.
c I.
is stirred for 20 days at room temperature with exclusion of
air. The solid reaction product [(CzH5)4P]CI is filtered off
and the ether removed from the filtrate under vacuum,
whereupon compound (2) remains as a colorless, spontaneously inflammable liquid (78 %yield): b.p. 36-38 "Cj5 x 10-4
torr, mol. wt. (cryoscopic, benzene) 169 (calc. 162.3). IR:
v,,SiH3 2090 cm-1. 1H-NMR (pure liquid, TMS as external
reference[sl): 6SiH3 -239, dd, J(HCSiH) 4, J(PCSiH) 8.5;
SCH +89. dq, J(PCH) 7; SCH2 -92, dq, J(H;?CP), 10.5;
SCH3 -59, dt, J(HCCP) 16.5, J(HCCH) 7.7.
In a similar manner we obtained:
(CH3)3P=CH-SiH3, m.p. -16"C, mol. wt. 115.2 (calc.
120.2). IR: va,SiH3 2100 cm-1. 1H-NMR (benzene, TMS as
external reference): SSiH3 -2.45, dd, J(HSiCP) 10.4 Hz.
J(HSiCH) 3.8 Hz; 6CH t 7 7 , dq, J(HCP) 6; 6CH3P -26, d,
J(HCP) 12.5 Hz.
(CH3)3P=C(SiH&, m.p. 11-13 "C, b.p. 24-25 'Ci4 x 10-2
torr, mol. wt. 143.5 (calc. 150.3). IR: va,SiH3 2102. 1H-NMR
(see above): GSiH3 -241.5, d, J(HSiCP) 10.2Hz; SCH3
-19.5. d, J(HCP) 12.5; J(IH13C) 127.5 Hz, J(1H29Si) 189 Hz.
Received: January 16, 1969
[Z 959 IE]
German version: Angew. Chem. 81, 329 (1969)
The critical last step is to be interpreted as a "transylidation"
of triethyl(silylmethyl)phosphonium chloride (Z) by triethylethylidenephosphorane. This reaction yields tetraethylphosphonium chloride and triethyl(siIylmethy1ene)phosphorane (2) almost quantitatively, thus proving the thermodynamic preference of the latter over the possible aIternative
product diethyl(ethylidene)(silylmethyl)phosphorane ( 3 ) .
Earlier experiments with substituted and unsubstituted ylids
have shown that the proton migration necessary for the conversion of (2) into (3) (particularly in the presence of the
corresponding salt) is kinetically feasible [41. Even a silyl
migration (2) 4 4 ) would be conceivable if it were thermodynamically advantageous [1*51. However, isomerization of
(2) to ( 3 ) or to ( 4 ) could be induced neither thermally nor
There is no explanation for the preference of (2) over the
other isomers on the basis of steric hindrance, nor of a simple
inductive effect in the G skeleton. I n this and in many other
cases the concept of a (p +d)x interaction currently represents the most promising theoretical model [61.
CICHzSiH3 (2.7 g, 34 mmole) is added over a period of 1 h
to ( C ~ H S ) ~
P g, 34 mmole) with cooling (methanol/Dry
Ice). A t -30 OC quantitative formation of quaternary salt
takes place spontaneously in a n exothermic reaction to yield
( I ) (6.7 g) as a white crystalline powder, m.p. > 340 "C. IR:
v,,SiH3 2180 cm-1. 1H-NMR (CDC13, 60 MHz, TMS as external reference 181): SSiH3 -240, dt, J(HCSiH) 4, J(PCSiH)
8.2; 8CHzSi -151. dq, J(PCH) 16; SCH3CH2 -161, dq,
J(PCH) 13, J(HCCH) 7.5; 6CH3 -88, dt, J(PCCH) 18.
(CzH&PCHCH3 (3.7 g, 25.4 mmole) is added to a suspension of ( I ) (5 g, 25.4 mmole) in ether (50 ml) and the mixture
Angew. Chem. internat. Edit. Vol. 8 (1969) 1 No. 5
[*I Prof. Dr. H. Schmidbaur and Dip1.-Chem. W. Malisch
Institut fur Anorganische Chemie der Universitat
87 Wurzburg, Rontgenring 11 (Germany)
111 Organosilicon Chemistry of Phosphorus Ylids, Part 7. Part 6: H . Schmidbaur and W. Malisch, Chem. Ber. 102,83 (1969).
[2] D. Seyferfh and ti. Singh, J. Amer. chem. SOC.87, 4156
(1965); D. Seyferth, ti. Singh, and R . Suzuki, Pure appl. Chem.
13,1596 (1966); D. Seyferth and S . 0 . Grim, J. Amer. chem. SOC.
83, 1610 (1961).
131 N . E . Miller, J . Amer. chem. SOC.87, 390 (1965); Inorg.
Chem. 4, 1458 (1965); D. R. Marhiason and N . E. Miller, Inorg.
Chem. 7, 709 (1968).
[4] H. Schmidbaur and W. Tronich, Chem. Ber. 100, 1032 (1967);
101, 595, 604, 3556, 3545 (1968); Inorg. Chem. 7, 168 (1968).
[5] Cf. e.g.: H . Schmidbaur and W. Tronich, Angew. Chem. 8C,
239 (1968); Angew. Chem. internat. Edit. 7, 220 (1968).
[6] E. A . V . Ebsworth: Volatile Silicon Compounds. Pergamon
Press, Oxford 1963; Chem. Commun. 1966, 530.
[7] The thermal dismutation affords, inter a h , compound ( 5 ) .
181 All values in Hz; negative signs for lower field (60 MHz).
FXeOTeF, : A Derivative of Xenon Difluoride
By F. SIadky [ *I
Xenon difluoride reacts with oxyacids such as HOSOzF,
HOC1O3, and HOPOF2 in the molar ratio 1 :1 with elimination of HF.
The xenon-containing intermediate products are thermally
unstable and decompose into the corresponding complex
peroxides and oxides (S206F2, C1207, P203F4) [II.
Pentafluoroorthotelluric acidczl, however, quantitatively
yields a stable xenon-containing reaction product:
Fluoroxenon pentafluoroorthotellurate is a pale yellow
liquid (b.p. 53 "Cj0.01 torr; m.p. -24 "C) which can be distilled without decomposition in a glass apparatus under vacuum. IR (liquid film between AgCl plates; 4000-400 cm-1):
768 (s). 704 (vs), 623 (s), 520 (m), and 470 cm-1 (m). The
19F-NMR spectrum indicates a value of 37 ppm for ~ T in~ F
the AB4 part of the OTeFs grouping and a value of 66.3 ppm
(CF3COOH as external standard).
for 8 x e ~
FXeOTeF5, like XeFz (31, can give up a fluoride ion to acceptors such as AsF5:
FXeOTeF5 -1 AsF5 + [FST~OX~]+[ASF&
Reaction of FXeOTeF5 with CsF proceeds via two routes in
almost equal proportions:
+ CsFf
TeF6 + (FXeO-Cs+) --f CsF
+ Xe +
Complex (3) is apparently more stable than (2). That the latter
is formed first under mild conditions shows that less activation energy is required for complex formation of chromium
with the olefinic x-electrons of ligand L (it is not necessary
to compensate for the loss of resonance energy).
Heating this product (3) for 20 hours with a large excess of
Cr(CO), in di-n-butyl ether enables a further Cr(CO), group
to be introduced, thereby giving the orange, non-sublimable
LCrz(C0)6 (4). which can be purified in the same way as (3)
(decomp. above 170 "C).
XeFz t Cs[OTeFd
All reactions were followed gravimetrically and tensimetrically in easily weighable Kel-F reaction vessels fitted with
Kel-F taps. Vacuum manipulations were carried out in a
Monel system. The XeFz used in the experiments was prepared photolytically 141. Reaction of 2.35 g (13.9 mmole) of
XeF2 with 3.33 g (13.9 mmole) of HOTeFS yields 5.20 g of
FXeOTeF5, yield 96 %.
Received: January 10, 1969
[ Z 960 IE]
German version: Angew. Chem. 81, 330 (1969)
[*I Dr. F. Sladky
Institut fur Anorganische und Analytische Chemie
der Universitat
A-6020 Innsbruck, Innrain 52a (Austria)
[l] N . Bartlett and F. Slndky, unpublished.
[2] A . Engelbrecht and F. Sladky, Mh. Chem. 96, 159 (1965).
[3] F. Sladky, P. A . Bulliner, N . Bartlett, B. G. DeBoer, and A .
Zalkin, Chem. Commun. 1968, 1048.
141 S. M. Williamson, F. Sladky, and N . Bartlett, Inorg. Syntheses
11, 147 (1968).
Dibenzo[u,e]cyclooctene Complexes of
Chromium and Molybdenum
Treating an excess of tris(acetonitri1e)tricarbonylmolybdenum(0) I41 with L in dioxane at 35 'C/15 torr for 2 hours
gives a 65 % yield (calculated on L) of tetracarbonyl(dibenz0[a,e]cyclooctene)molybdenum(0), LMo(C0)4 / 5 ) , which
forms pale greenish-yellow crystals of m.p. 170 "C (decomp.).
It has not yet proved possible to convert this into a complex
analogous to ( 3 ) ; instead, heating it in di-n-butyl ether for
6-8 hours leads to separation of decomposition products and
formation of the lime-green cis-dicarbonylbis(dibenzo[a,e]cyclooctene)molybdenum(O), cis-LzMo(CO)z ( 6 ) , m.p.
215 OC (decomp.). The contrasting behavior of chromium
and molybdenum expresses clearly the differing tendencies
of these metals to formation of x-aromatic and x-olefinic
By J. Miiller, P. Goser. and M. EIian[*l
Most of the x-aromatic complexes of chromium are considerably more stable than its x-olefin complexes. For instance,
reaction of Cr(C0)6 with 1,4-diphenylbutadiene leads exclusively to tricarbonyl(l.4-diphenylbutadiene)chrornium(O)
( I ) [1,21.
The constitutions of the new complexes were proved by
elemental analyses, mass spectra [61, the number and positions of the vco vibrations, and the IH-NMR spectra
For steric reasons the olefinic x-electron system of dibenzo[a,e]cyclooctene [31 (= L) seems to be considerably better able
to form complexes with chromium than is that of butadiene,
and by its use we have been able to provide the first example
of x-aromatic and x-olefin complexes from one ligand.
If the compound (L) is treated with tris(acetonitri1e)tricarbonylchromium(0) [41 in 5-6-fold excess in di-n-butyl ether
for 2 hours at 40 OC at water-pump vacuum and the ether is
then removed and the residue eluted with warm hexane, the
resulting solution affords crystals of the yellow tetracarbonyl(dibenzo[u,e]cyclooctene)chromium(O), LCr(C0)4 (2), m.p.
141-143"C, in 90% yield (calculated on L). This can be
sublimed almost without decomposition at 80-100 "C in a
high vacuum and is thermally more stable than tetracarbonyl(1,5-cyclooctadiene)chromium(0)~5~.However, when heated
in n-decane or di-n-butyl ether at 140°C, (2) loses CO during
1.5 hours to form yellow tricarbonyl(dibenzo[a,e]cyclooctene)chromium(O), LCr(CO)3 ( 3 ) , m.p. 168-17OoC, that
is purified by chromatography on silicagel in benzene and
recrystallization from rnethylene chloridejhexane.
[a] In deuterioacetone.
Angew. Chem. internat. Edit.
I Vol. 8 (1969) I No. 5
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fxeotef5, difluoride, xenon, derivatives
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